To begin with, let us recall some basic facts about plant nutrition. Green

plants obtain raw materials for their biosynthetic processes in rather

simple forms: carbon dioxide, water, nitrate, phosphate, and ionic forms of

potassium, calcium, and other essential elements. Nitrogen, to choose a

particularly contentious example, almost always enters the roots as nitrate,

becoming assimilated by the plant’s biochemistry into organic compounds

such as amino acids and nucleotides. There is no doubt, then, that nitrate

is a “natural” plant nutrient. Nevertheless, a strict organic farmer does not

wittingly fertilize his crops with nitrate – or with ammonium salts, which

are quickly converted to nitrate by soil bacteria.

Why should a natural plant nutrient such as nitrate be regarded as

unnatural when added to the soil as fertilizer? To appreciate this

argument, we need to go back into soil ecology beyond the immediate

entry of nitrogen into the roots. In a natural system, nitrate in the soil is

derived from the gradual breakdown of humus, the dark, complex,

polymeric material that gives the soil its “tilth.” Nitrogen is integrally bound

to the carbon atoms that make up the organic structure of humus, which

is itself the end product of a complex chain of events that carries nitrogen

into the soil. The main path of entry begins with the deposition of organic

nitrogenous compounds on the soil in the form of animal feces and urine

and the dead remains of animals and plants. These largely organic

materials are subjected to hydrolytic and oxidative degradation by decay

microorganisms, yielding organic low-molecular-weight products that

support the growth of microbial flora. These processes finally yield a mass

of microbial cells, which on their death, together with some other remains,

become humus. The other source of soil nitrogen is nitrogen fixation,

which also delivers the element to the soil system in organic form. Thus, in

a natural soil system, untouched by human technology, nitrogen enters

into the system in organic combination with carbon, largely as the

nutrient for microorganisms that eventually produce humus.

Now a farmer who wishes to add nitrogen fertilizer to the soil to support

crop nutrition has two main alternatives. Nitrogen can be added in a

natural, organic form – as plant residues, manure, sewage, food wastes, or

for that matter, in the form of any nitrogenous organic compound that

can be metabolized by the soil’s microbial flora and thereby yield humus.

Alternatively, nitrogen can be added in an equally natural, but inorganic

form, such as nitrate or ammonia. The first choice is the one made by the

organic farmer; the second is the conventional route of modern

agriculture technology. The strict devotee of natural foods is likely to

reject grain grown with inorganic fertilizer in favor of that grown

“organically” with manure or compost, sometimes claiming that the

nutritional value and keeping qualities are superior – a claim that at this

point can neither be confirmed or denied.

Is there, then, any point in differentiating between the two ways of

supplying fertilizer nitrogen? Indeed there is. Considering the soil as an

integrated system, there is a vast difference in the outcomes of the two

methods. Because nutrient uptake is a working-requiring process, it must

be driven by the root’s oxygen-dependent energetic metabolism. Humus is

much more that a store of nutrients; it is also the chief source of the soil’s

porosity, hence of its oxygen content, and therefore of the efficiency with

which nutrients, such as nitrate, are taken up by the crop.

Thus, the critical difference between the alternative means of supplying

nitrogen fertilizer is that the organic form leads to the production of

humus, while the inorganic form does not. The use of synthetic urea as a

fertilizer provides an informative test of this distinction. Urea is, of course,

an authentic organic compound and is, in fact, an ordinary constituent of

a clearly natural source of nitrogen – urine. The scientific agronomist may

often cite the organic farmer’s objection to pure urea as a fertilizer – it is a

fairly common one in modern agriculture – as evidence of the irrational

basis of organic farming. But is it?

While urea is, indeed, an organic compound, it will not support the

bacterial growth that is essential for the formation of humus. When urea is

metabolized, the products are ammonia and carbon dioxide. Thus, urea

yields carbon in a form that will not support the oxidative metabolism of

solid bacteria. To accomplish that, carbon must be in the reduced state,

combined with hydrogen, as it is in the nearly all more complex organic

compounds. Although urea is an organic compound, by failing to support

the growth of soil bacteria, and therefore the formation of humus, it does

not qualify as an “organic fertilizer.”

The intensive use of inorganic nitrogen fertilizer (or urea) may so overload

a humus-depleted soil with nitrate as to cause it to leach into surface

waters when nitrate levels may readily exceed public health standards.

Leached nitrate also wastes expensive fertilizer synthesized from an

increasingly diminished supply of natural gas. Apart from any other

possible and yet to be established virtues, the use of organic fertilizer (as

defined above) avoid these difficulties and holds the promise of restoring

the natural source of soil fertility – humus. While it remains to be seen

whether food grown in such naturally fertile soil contributes distinctively

to the health of people, the practice can, it seems to me, contribute

significantly to the health of the soil and the economy.

Dr. Barry Commoner

Director, Center for the Biology of Natural Systems

Used with permission from Hospital Practice magazine

Vol. 10, No. 4

At Geo Growers we get so many questions about turf grass

it’s hard to know where to begin. The best place to start is to

ask what you want to end up with; how easy is it to maintain,

and, most importantly, how much water will it require? Quite

often, the most recommended grass is the most

disappointing. Here I am speaking of Buffalo grass. Yes, it’s

the most drought tolerant of all grasses but it will not take

foot traffic, it will not grow in the shade, and the soil you

plant it on top of must be relatively fertile and weed free or

the weeds will take over. You must also be prepared not to

mow it. That may seem like a strange drawback for a turf

grass but here’s what happens: A few weeds show here and

there in a stand of buffalo and the caretaker makes a decision

to mow rather than pull, this is the beginning of then end.

Once the grass is cut it loses its competitive advantage of

shading the soil. The weeds can handle the hotter drier soil

and they quickly make use of the increased light. After a few

more mowings it will not look like the original vision of a

prairie.

This weed problem can be avoided of course with the

placement of a two-inch layer of a weed-free, fertile soil blend.

This excludes Sandy Loam, which has no water holding

capacity, leaving it a mud pie under wet conditions and a

brick when dry. This material is so totally dead and infertile

that it becomes a waste of money to amend it. Living soils

must have organic matter in them in order to support

microbial life, hold water, and recycle nutrients, especially

nitrogen. Sandy Loam’s high PH rating, 9.4 in some cases,

destroys organic matter. The caretaker winds up having to

fertilize often, use toxic substances to control pests and

weeds, as well as water all the time.

With the correct soil none of this would be necessary. A living

soil enables a lawn to go long spells between watering, never

needs fertilizer, and never ever needs toxic rescue chemicals

which will poison our well water and stock tanks. Next month

more on turf grass selection.

Turf Grass Selection (Article #2)

Just as I promised there will be more discussion on turf grass

selection this month. However, now is an excellent time to

explore the fundamentals of soil structure and function as it

pertains to turf grass production. Understanding these things

will lead us directly to the satisfaction and bliss that comes

from that sea of green turf grass that we grow ourselves.

Any turf grass can be considered as a crop, and, as such,

requires real fertility to overcome weeds and to be able to

handle environmental stresses such as too hot, too cold, too

wet, too dry, too much foot traffic etc. Consider the fertility

factor of “loft.” Loft is how fluffy a soil is. How fluffy it is, is a

factor of how easy it is for a grass to grow its roots and

runners through it. Loft is also a factor of how easily a soil will

absorb water, as opposed to it running off into the creek

along with the fine particles of your remaining topsoil. Loft is

also a factor of how soil breathes. That’s right, you read it

right, how soil breathes. Soil breathes? How does it do that,

and why is that necessary? The microbial life in the soil, the

ones that live in symbiosis with the grass roots (and many

others) are air-breathing microbes. They must have a fresh

supply of oxygen to digest carbon for energy and do the

work of transporting water, foods, and minerals into the

plant’s root system. If the available oxygen is limited, the work

the microbes do is also limited. For the plants (turf grass in

this case) the limited microbial activity means less water,

nitrogen, trace minerals, phosphorous, calcium, and all the

rest. The plants growth slows down, it loses its vigor. Weeds,

pests, and pathogens can and will take advantage of this.

Oxygen rich soils counter all this mayhem and make your

lawn healthy and strong.

So how does this fluffy soil breathe you ask, having never

seen it heave up and down, at least not while you were

looking. It breathes, so to speak, with changes in barometric

pressure, even minute changes. This is what pumps air into

and out of the soil. Oxygen is not the only gas going in and

out of the soil; there is also nitrogen, and that’s free nitrogen

for your crop or turf grass. There are microbes not associated

with legumes that also fix nitrogen into the soil and make it

available to plants. These are called azotbactor microbes.

This one factor referred to as soil loft is probably the most

unsung hero of soil fertility. Next month more on turf grass

selection.

Turf Grass Selection (Article #3)

As promised, this month we’re going to talk about turf grass

selection. The best question, as always, is: “What do you want

it to do?”

We’ll start with the amount of water it will use. The real

question is how much water you’re going to put on it –

enough to keep it green or just enough to keep it alive? For

all four turf grasses (Buffalo, Zoysia, Bermuda, St. Augustine),

the answer is “none” to “a lot ” depending not on the type of

grass but the soil under it. For example, there is a home in

Oak Hill that has had a lawn around it for 25 years. In this

area there have been some pretty tough droughts in that

time period. However, in all that time, the owners have never

watered it. Or fertilized it, or poisoned it, for that matter. They

don’t do anything for their yard except occasional mowing.

So what is this grass? It’s St. Augustine! That’s impossible,

right? Everything you’ve heard says that can’t be true.

Remember that the success or failure of plant life is a

reflection of the soil ecology that sustains it. This lawn is

planted on rich bottom land – in this case, pecan bottom. The

shade from the trees is also a factor. You could not grow

Buffalo grass and Zoysia wouldn’t do very well. So how

brown does the grass get in a drought with no one watering

it? Pretty brown, certainly, but its resilience is sustained by

the living soil underneath it. That rich soil is what creates a

drought-tolerant lawn of St. Augustine grass. And how,

exactly, did they do that? Simple! They didn’t water it.

Next month we’ll continue the selection process by

examining such things as the amount of foot traffic expected.

That includes all kinds of feet: dogs, kids, party guests,

neighbors, militant pamphlet distribution agents, and other

assorted groups of curious onlookers.

‘Til then, HAPPY LANDSCAPING!

Turf Grass Selection (Article #4)

The selection process for turf grass, based on “What do you

want it to do?”, has now reached the question of foot traffic.

Buffalo grass, while beautiful to look at from a distance looks

lousy up close after a party or a Bar-B-Que. It looks obviously

trampled and does not recover quickly. Zoysia fairs much

better, however it does not bounce right back after an event.

Bermuda will show signs of being walked on and is very

reliable when it’s time to re-grow and recover. However,

Bermuda is not much fun to play on (for kids and adults

alike), walk on or romp on because it’s so thin. Bermuda grass

has no cushioning effect. When it comes to foot traffic,

recovering from parties, romping and rough-housing one

grass stands out from the rest. That grass is St. Augustine.

I’m not just speaking from my own experience; this is the

same answer I get from professional lawn maintenance

providers. Every time I ask that question the answer that

comes back is always the same, “Yeah, if you want a grass

that stands up to foot traffic, St. Augustine is it.”

The people I’m asking this question of are knowledgeable

and experienced professionals who have been in business a

long time. These are not the kind of people who lower their

lawn mowers in hot weather just because the grass stopped

growing and they want to make it look like they did

something.

Now that the subject of “How tall should the grass be?” has

been brought up, let me say that it is an intricate and

important part of water conservation, soil health, and the

subject of next month’s column. This is also taking us in the

direction of why water conservation is connected to

traditional water rights and why that is becoming a hot, if not

explosive political issue.

Till’ next time, HAPPY LANDSCAPING

Turf Grass Selection (Article #5)

How tall should turf grass be? Well, what do you want to end

up with? Something nice to walk on? The manicured look?

Easy maintenance? Minimum water usage? The best place to

start is with a look at the physics of light and heat. When

sunlight reaches the surface of almost any given object it is

absorbed and turned into heat. Heat is a form of light

(infrared) that can travel through solid matter, i.e. rocks,

concrete, pavement, bricks, soil, shoestrings, soap bubbles;

you name it and heat can move through it. Heat moves faster

through things that are dense and slower through things

that are fluffy. There are, however, instances when light is

absorbed that it does not become heat.

Say for instance when light strikes a green leaf or blade of

grass. What happens next is a wonder, a miracle, an event so

awesomely complex that no computer yet devised can track

even one second’s worth of activity taking place within a

single cell of the simplest plant. What we do know however,

is that instead of turning into heat the light is used via the

agency of chlorophyll, to make sugars, carbohydrates, fats,

and proteins which are organized into larger structures

called plants. In short, light is used to drive the biological

machinery of plants instead of turning into heat. The rest of

us life forms who cannot do this are deeply in their debt.

If you have a lawn of green grass, light striking it is used up

powering the biological reactions that grow the grass. Some

of the light reaches the soil and is turned into heat. Taller

grasses mean more light is used up driving biological

processes and less is absorbed by the soil and turned into

heat. Cooler soil means soil that holds more water. Soil that

holds adequate water not only provides for the needs of the

plant populations growing in it and on it (not just grass), but

also becomes a hospitable habitat for a very large array of soil

microbes. As mentioned earlier these air breathing microbes

do the work of making nutrients available to plants. Taller

grasses, cooler soil, greater water retention, and better soil

ecology.

1. Turf grass is generally grown within a monoculture system, and

as such, has a delicately balanced ecosystem.

2. All too often, lawns have way too much phosphorus (P) and

potassium (K), and not nearly enough nitrogen (N).

3. Carbon-depleted soils cannot effectively hold nitrogen for the

length of time it takes roots to absorb it; thus, it runs off, dissolved in

water, or floats off in the wind as it gasifies.

4. Fertilizer programs worsen soil conditions because they do not

put back carbon, which feed microorganisms and keeps soil fluffy

and gas-permeable. Soils that are fluffy are said to have loft. Soils

that have loft are said to be gas-permeable. Gas-permeable simply

means that soils have an air exchange rate between the atmosphere

and the soil that is great enough to sustain microbial life below the

surface.

5. How well a soil breathes, i.e., how deeply and how thoroughly, is

a function of how much and what types of carbon are present.

Types of Carbon Present in Healthy Soils

1. Sugars created by plants through photosynthesis and exuded

through their roots feed the microbial life colonizing the roots of the

same plant. These are the “heart-pounding, thrill-a-minute,

makes-life-worth-living” forms of carbon that sustain the relationship

between plants and the beneficial microbes on their roots.

2. Carbohydrates, starches, and cellulose, which come from plants

or parts of plants that have died and fallen into the soil, are more

complex and enduring forms of carbon that not only serve as food

for the soil food web, but also provide structure.

3. Polysaccharides and lignins, the most durable of all the carbon

structures, along with other features of the soil, form the

foundation for “soil horizons.”

4. These soil horizons represent different “divisions of labor,”

organizing themselves into different horizontal layers.

5. All the forms of carbon within the soil layers serve multiple

functions:

* They provide loft so that soil breathes and microorganisms get

oxygen.

* They attract, absorb, and hold water for plants and

microorganisms.

* They attract, absorb, provide, and disperse minerals and

nutrients for microorganisms and plants.

* They provide surface area and structure for microbial activity

and plant root development.

6. The life of the soil is dependent on these four factors:

* Oxygen

* Water

* Food-sugars, carbohydrates, amino acids, and other raw

materials

* Structure and shelter

1. Mow your grass as high as the mower will allow. The taller the

grass, the more roots will develop below the soil. The taller the grass,

the cooler the soil will be. Cooler soil means more enzymatic activity.

And more enzymatic activity means more vigorous plant and animal

life (e.g., microbes and earthworms).

2. Let your lawn clippings lie. The clippings are mostly carbohydrate,

protein, and trace minerals. These materials shrivel up and fall back to

the soil, where they are consumed by the microbial life. Microbial life

forms expand and proliferate, fueled by the carbon and nourished by

the protein and trace minerals. When all the food is consumed, these

populations die back and yield the protein of their decaying bodies

back to the roots of the turf grass as nitrogen. Cooler soil

temperatures prevent the nitrogen from gasifying and facilitate the

uptake of the nitrogen by the grass roots. Additionally, nitrogen can

dissolve itself into water being held in the soil. All the trace minerals

and major plant nutrients (calcium, phosphorus, potassium, etc.) are

also recycled in this way.

3. Stop over-fertilizing your lawn. In many cases, this means stop

fertilizing your lawn altogether until you have a soil analysis done. In

a recent survey of two hundred lawns in Austin, turf soils had

dysfunctionally high levels of phosphorus and potassium and almost

no nitrogen. Nitrogen likes to be a gas – it either dissolves into water

and moves away from soils that have no water-holding capacity, or

quickly evolves into a gas in hot soils and floats away in the breeze.

The phosphorus and potassium, being minerals, are left behind and

can become a serious problem as residues build up.

4. Keep your lawn mower blade sharp.

5. Top-dress your lawn with materials that will increase water-holding

capacity and organic matter content.

6. Feed the soil, not the lawn. Healthy soil will always produce healthy

turf grass. Use products such as alfalfa pellets, Medina Soil Activator,

Aggrand, Alaska Fish Fertilizer, Texas Tee Soil Food, Maxicrop

Seaweed Fertilizer, and Maestro Gro Agricultural and Horticultural

Molasses. Fertile soil also eliminates the need for weed control -

weeds don’t stand a chance against vigorously growing turf grass.

7. Do not water in the heat of the day.